Laser level tripod thread ?
britishtrident - 20/12/05 at 05:07 PM
Mini project under way an ultra simple locost but highly accurate toe-in guage, It will be really just a very small version of the old Dunlop optical
tool but using a pocket laser level for the optics.
I need info on the threads used in Laser level tripod fixings am I right in thinking for some strange reason it is 1/4" Whitworth as I seem to
recall all camera tripods are.
[Edited on 20/12/05 by britishtrident]
Genesis - 20/12/05 at 05:10 PM
They are 1/4 Whit yes - Jap's are updating to ISO 5mm as found on a few new video camera 
MikeR - 21/12/05 at 12:12 AM
don't suppose you'll be posting the plans once you've figured it out???
britishtrident - 21/12/05 at 01:42 PM
Initial idea
MikeR - 21/12/05 at 05:16 PM
how do you measure the amount of toe though? would 1mm equate to the same angle every time? if so, what does 1mm equate to?
is the key bit getting the mirror and laser square to the wheel?
britishtrident - 24/12/05 at 03:20 PM
quote:
Originally posted by MikeR
how do you measure the amount of toe though? would 1mm equate to the same angle every time? if so, what does 1mm equate to?
is the key bit getting the mirror and laser square to the wheel?
The key is simple zero setting before each use, it dosen't really matter (within reason) if the mirror is set up exactly square as long as when
zeroed the laser beam reflects back exactly on itself --- angle of incidence = angle of relection. Therefore it will reflect exactly back on itself
only when the laser is at exactly 90 degres to the mirror.
Really pretty straight forward just trig using similar triangles -- much easier putting some real numbers in
Most wheels on cars have a tyre outer diameter of 20" to 24" -- typical locost front might be 20" = 500mm
Lets assume that the track width across the outer faces of the tyres is 60" = 1.500 mm
The mirror and laser are set slightly back say 250mm from the tyre.
We have to also multiply by a factor of 2 because we are measuring from a reflected beam.
The toe-in we want is in the range 0 to 3 mm measured on the outer circumfrence of the tyre
Using similar triangles to find the deflection.
3x((1500+250)/500)x2 = 21
3mm toe-in will give 21mm deflection of the beam -- guage factor multiplier of 7
If we use the guage on a car with a different track width and tyres the numbers will be different but not by that much -- just a matter of calculating
the new gauge factor.
[Edited on 24/12/05 by britishtrident]
britishtrident - 24/12/05 at 03:29 PM
This link to a pdf file is the instruction for a tool that works on the same general principle -- the documents explains how to zero before
use.
http://www.sealey-tools.co.uk/instructions/GA50.PDF